Re: Reading Commodore 900 disks in the 8250 (LP)

From: Michal Pleban <*lists_at_michau.name*> Date: Thu, 11 Jan 2024 14:15:29 +0100 Message-ID: <45944f2c-5b68-5cb8-2ea2-7f9ea8f4dd36_at_michau.name> · lists_at_michau.name

Francesco Messineo wrote on 11.01.2024 13:14:

> if it supports only GCR (I assume the same format as the 8250?) then
> why you need to bother with MFM ?

I do not :) I only want to read existing C900 GCR disks.

> If you know the actual format used it's easy to tell what is the
> mechanism they used, if it's 80 tracks per side, then it's 96 TPI, if
> it's 77 tracks per side, then it's 100 TPI.

According to the disk controller ROM disassembly it's 80, so it would 
point towards 96 TPI unfortunately :(

https://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c900/fd_disassembly.txt

Regards,
Michau.